The present invention relates to a superposed image display device which displays a plurality of images, particularly a plurality of images obtained by a plurality of different image diagnostic apparatuses.
Conventionally, as medical image diagnostic apparatuses, there have been known X-ray diagnostic apparatus, ultrasonic diagnostic apparatus, X-ray CT apparatus, nuclear-medicine diagnostic apparatus, digital radiography apparatus, NMR CT apparatus, etc. In the X-ray CT apparatus, a distribution of X-ray absorption coefficients on the cross sectional plane of a subject is obtained. In the nuclear-medicine diagnostic apparatus, a distribution of a dosed radioactive isotope is obtained. In the digital radiography apparatus, an X-ray fluoroscopic image is converted into digital data and is subjected to image processing. In the NMR CT apparatus, a distribution of hydrogen atomic nucleus is obtained due to nuclear magnetic resonance. In general, in order to securely diagnose the disease of a subject, it is desirable to photograph the same part by a plurality of image diagnostic apparatuses and to complementarily use the images of the same part having a plurality of different organism information, thereby synthetically diagnosing the disease.
For this purpose, an image display device to display a plurality of images is needed. Primitive viewing boxes are known wherein image films obtained from a plurality of image diagnostic apparatuses are arranged on a frosted glass on top of the viewing box (schaukasten) and the doctor watches and compares them. As other more advanced display devices, there is known a display device in which the images obtained from a plurality of image diagnostic apparatuses are arranged and displayed in one frame (multiframe display), and a display device in which the contour of another image is overlapped on one image and they are together displayed.
However, the multiframe display is effectively the same as the viewing box on which a plurality of images are arranged. Therefore, it is difficult to intuitively grasp the positional relationship between the plurality of images.
In addition, according to the contour display device, although the mutual positional relationship can be easily grasped, it takes a long calculation time to extract the contour and the contour lacks the detailed information which the original picture inherently has; consequently, it is impossible to promptly and accurately diagnose.